The present invention is directed generally to processes for the preparation of aryl amine polycondensation polymers, and photoconductive imaging members thereof. More specifically, the present invention is directed to processes for the preparation of poly(ethercarbonates) which can be selected as a charge transport layer in a layered photoconductive imaging member with a photogenerating layer and a supporting substrate, reference for example U.S. Pat. Nos. 4,801,517; 4,806,444 and 4,806,443, the disclosures of which are totally incorporated herein by reference.
In embodiments, the present invention relates to the preparation of aryl amine poly(ethercarbonates) PEC by the utilization of interfacial polymerization, and the use of a water miscible cosolvent, like dioxolane to thereby simplify the procedure by avoiding a heating step to effect dissolution of the water soluble monomer and avoid undesirable oxidation effects, and wherein aryl amine poly(ethercarbonate) polymers with a high molecular weight can be obtained, for example 350,000. U.S. Pat. Nos. 4,806,443 and 5,028,687, the disclosures of which are totally incorporated herein by reference, disclose aryl amine poyl(ethercarbonates), a solution polymerization process for the preparation of aryl amine poly(ethercarbonates), and the use of these polycarbonates in imaging systems.
Illustrated in copending application U.S. Ser. No. 036,162 (D/91424), the disclosure of which is totally incorporated herein by reference, are methods for the preparation of poly(ethercarbonates) wherein a water miscible cosolvent is not selected, and more specifically there is illustrated in this application a process for the preparation of aryl amine polycondensation polymers useful in electrophotographic imaging members, which process comprises the interfacial polymerization of an aryl amine diol dissolved in an alkaline aqueous phase with a bifunctional acid halide dissolved in an organic solvent, resulting in polymers with high molecular weight and narrow molecular weight distribution (M.sub.w /M.sub.n) of from between about 50,000 to about 350,000, and a M.sub.w /M.sub.n of from about 1 to about 4. By not using a water miscible cosolvent, the aqueous phase is heated to from about 75.degree. to 95.degree. C. to dissolve the dihydroxyaryl amine compound in an alkali media. During this heating step, oxidation of the dihydroxyaryl amine may result. In the present invention in embodiments, by using a water miscible cosolvent, the need to heat up the aqueous phase is eliminated thereby rendering the process much simpler. Also, disclosed in the aforementioned copending application is a process for the preparation of polycarbonates which comprises the interfacial polycondensation reaction of an alkali metal hydroxide, an aryl halide, and an aryl amine, followed by the addition of an alkyleneglycol bishaloformate; separating the organic phase from the alkali water phase comprised thereafter precipitating the product in an aliphatic alcohol, and isolating the polymer product therefrom.
The present invention relates to interfacial polymerization, and the use of a water miscible cosolvent for the synthesis of the aforementioned aryl amine poly(ethercarbonates). With interfacial polymerization instead of solution polymerization, there is enabled certain molecular weight polymers with narrow molecular weight distributions (MWD). Also, a significant improvement in the mechanical properties, including wear resistance, is obtained with the products obtained with the processes of the present invention. For example, the wear resistance of imaging members containing the polymers of the present invention is improved by a factor of about 2 to 3 as compared to a typical photoreceptor with a charge transport layer comprised of charge transporting small molecules, such as N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine dissolved or dispersed in various polymers, such as polycarbonates like bisphenol A polycarbonate, including MAKROLON 5705.RTM.. One embodiment of the present invention is directed to an imaging member comprised of a supporting substrate, a photogenerating layer comprised of photogenerating pigments in contact therewith, and a charge, especially hole, transport layer comprised of the aryl amine poly(ethercarbonates) obtained with the processes as illustrated herein. The aforementioned imaging members are also useful in liquid development systems in that, for example, the members thereof can be resistant to liquid developer components containing hydrocarbon type solvents, such as ISOPAR.RTM. and NORPAR.RTM., in that, for example, they retain their electrical and mechanical characteristics for extended time periods.
U.S. Pat. No. 4,806,443 describes a solution polymerization process for the preparation of aryl amine poly(ethercarbonates). Solution polycondensation involves the reaction of a dihydroxy aryl amine with a glycol bischloroformate in an appropriate solvent and in the presence of an organic base. With the solution process, there results polymers with relatively low molecular weights, such as from between about 40,000 to about 150,000. For example, when a high purity dihydroxyaryl amine monomer is used and when the dihydroxyaryl amine monomer selected contains small amounts of polyfunctional impurities, the polymer obtained can have a high molecular weight (M.sub.w over 200,000), and the molecular weight distributions, (M.sub.w /M.sub.n or MWD) are wide, of the range 3 to 12. Materials with these molecular weights and large molecular weight distributions can suffer from poor mechanical performance criteria, such as excessive wear and cracking, in photoreceptor applications. For purposes of increasing the molecular weight from 200,000 to about 300,000, and thereby improving the mechanical characteristics of the polymers obtained, there is introduced during the polymerization reaction thereof crosslinking agents such as 1,3,5 -benzenetricarbonyl trichloride, tri(4-hydroxyphenyl)ethane or 3,3',3",3"'-tetrahydroxytetraphenyl-benzidine. However, the use of crosslinking agents causes difficulties in controlling the molecular weight, can cause problems in electrical properties of the polymer, and cause difficulties in processability, due to increases in solution viscosities. In attempts to reduce the molecular weight distributions and thus improve the mechanical properties of these materials, fractionation of the materials is carried out, generally by the selective precipitation of higher molecular weight polymer. This can result in poor yields of the desired polymer. These and other disadvantages are avoided, or minimized with the polymers, such as polycarbonates obtained with the processes of the present invention.
Photoresponsive imaging members are known, such as those with a homogeneous layer of a single material such as vitreous selenium, or composite layered devices containing a dispersion of a photoconductive composition. An example of a composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006, which discloses finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder.
Photoreceptor materials comprising inorganic or organic materials wherein the charge generating and charge transport functions are performed by discrete contiguous layers are also known. Additionally, layered photoreceptor members are disclosed in the prior art, including photoreceptors having an overcoat layer of an electrically insulating polymeric material. Other layered photoresponsive devices have been disclosed, including those comprising separate photogenerating layers and charge transport layers as described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Photoresponsive materials containing a hole injecting layer overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin, are disclosed in U.S. Pat. No. 4,251,612, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in these patents include trigonal selenium and phthalocyanines, while examples of transport layers include certain aryl diamines as illustrated therein.
Layered photoconductive imaging members useful with liquid development systems are illustrated in U.S. Pat. Nos. 4,801,517; 4,806,443 and 4,806,444, mentioned herein.
Documents illustrating layered organic electrophotographic photoconductor elements with azo, bisazo, and related photogenerating compounds, and charge transport layers, which may be dispersed in polycarbonates in some instances, include U.S. Pat. Nos. 4,390,611, 4,551,404, 4,596,754, Japanese Patent 60-64354, U.S. Pat. Nos. 4,400,455, 4,390,608, 4,327,168, 4,299,896, 4,314,015, 4,486,522, 4,486,519, 4,555,667, 4,440,845, 4,486,800, 4,309,611, 4,418,133, 4,293,628, 4,427,753, 4,495,264, 4,359,513, 3,898,084, 4,830,944; 4,820,602; and 3,898,084; the disclosures of each of the aforementioned patents being totally incorporated herein by reference.